1. Field of the Invention
The present invention relates generally to a bicycle, and more particularly to an auxiliary power device of a bicycle.
2. Description of the Related Art
In early time, bicycles are nothing but a cheap transportation. In present days, automobiles and motorcycles replace bicycles to be the main transportation means. For a rising of health and recycling issues, however, bicycles become a tool for body fitness and exercise. When petroleum prince rose sharply in 2007 to 2008, riding bicycles further have a meaning of saving power. Until now, more and more people cycle for work or for exercise in holidays.
Typically, the bicycles are equipped with a transmission to meet various roadways. However, cycling in mountain roads or cycling for a long distance still is a heavy loading for riders. There are electric power bicycles in the market which equipped with a battery and a motor that the rider may switch manually for cycling by feet or by motor. However, the battery and the motor are heavy and huge, and the battery power is limited that only elder people choose the electric power bicycles.